Often I have been starting with a scout -> slinger -> warrior. Then Whatever follows depends on what information I get. Scouts I find invaluable not just for scouting but for early wars too, If I do start an ancient war I like to have two scouts actually, though I usually get one from a hut. Not only are they great for catching builders and settlers, but they can also be used to quickly get behind a city to encircle it, to screen the movements and exert zone of control for more valuable archers, act as decoys or as sacrifices when needed, pillage improvements/trade routes, and catch an enemies running away with a sliver of health. My success in ancient wars has skyrocketed since I started using them actively in fights. The extra movement they get is just too vital to pass up when dealing with archers, any other unit will get shot to pieces the moment they hit a forest or mountain. Scouts go where they want and do what they please.
They're kind of like cavalry before you get cavalry. I like using them so much I actually wish there were a civ with a unique scout.